Last time while I was hacking away at my case with my Dremel Multi-Pro, something happened where the tool itself would not vary in speed. 

It would just start up at 30,000 rpms no matter what the setting I change it to.  Not very helpful when cutting plastic, instant melting. So I thought great, what would I do now with a broken Dremel:

   One of our visitors by the name of eipromb, suggested that I crack open the tool and clean the rheostat, the part that controls the speed.  Now since I love breaking things, I thought what the hell it can't get any worst than this.  So I took the four screws out and went searching for the rheostat. It isn't very hard, its right where the speed switch is and its bright red. Anyway, I grabbed my QTip and proceeded to wipe away at the dirt and grime:

  Just give it a couple of swipes making sure that you get all the dirt out.  Screw the little tool together, plug her in and you have yourself a working Dremel again! At least I did : ) So if you're ever in my position where your Dremel just won't vary in speed, give it a clean, it might help! 

   If you find that this small minute guide helpful, please let me know.  Thanks again for that reader who sent in this suggestion